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	<title>2443：[Usaco2011 Open]奇数度数 </title>
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		<a class="header-logo header-affix-hide margin-left-no margin-right-no" data-offset-top="213" data-spy="affix">[Usaco2011 Open]奇数度数 </a>
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                [Usaco2011 Open]奇数度数                 </h1>
                <p>时间限制：10s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：128MB</p>			</div>
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                                <h3>题目描述</h3><p><p><br />
奶牛们遭到了进攻！在他们的共和国里，有N(1 &lt;= N &lt;=50,000)个城市，由M<br />
(1 &lt;= M &lt;= 100,000)条无向的道路连接城市A_i和B_i(1 &lt;= A_i &lt;= N;<br />
1 &lt;= B_i &lt;= N;A_i != B_i; 不会有重复的道路出现)。然而，整个共和国不一定是<br />
连通的&mdash;&mdash;有一些城市无法到达另外一些城市。<br />
<br />
入侵者想得到共和国的地图。(入侵者很傻，因此，他们的绘制地图的方法是去访问<br />
每一条边，T_T)。奶牛想要折磨一下入侵者，使得他们尽可能难地完成地图绘制。因此，<br />
奶牛会破坏若干条道路。<br />
<br />
请你帮助奶牛找到一个道路的子集，使得每条边每个点的度数为奇数。或者输出不存在这<br />
样的一个子集。(奶牛的图论学得真好.= =||)<br />
<br />
举个例子，考虑下面的共和国：<br />
<br />
1---2<br />
\ /<br />
&nbsp; 3---4<br />
<br />
如果我们保留道路1-3,2-3和3-4,破坏道路1-2,那么城市1,2,4都只有一条边相连，城市3有<br />
3条边相连：<br />
<br />
1&nbsp;&nbsp; 2<br />
\ /<br />
&nbsp; 3---4<br />
<br />
</p></p><hr/><h3>输入格式</h3><p><p><br />
* 第一行：两个用空格隔开的整数：N和M<br />
<br />
* 第二行到M+1行：第i+1行有两个空格隔开的整数A_i和<br />
<br />
</p></p><hr/><h3>输出格式</h3><p><p><br />
* 第一行： 一个整数表示需要保留的道路数量</p>
<p>* 第二到K+1行：每行一个数表示保留的道路的编号，范围是1...M。<br />
</p></p><hr/><h3>样例输入</h3><pre>4 4
1 2
2 3
3 1
3 4

</pre><hr/><h3>样例输出</h3><pre>3
2
3
4
</pre><hr/><h3>提示</h3><p><p>本题需SJ请不要提交！</p></p><hr/><h3>题目来源</h3><p>Gold</p>
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